1891.] 
333 
[Davis. 
of certain volume and slope, the form of its curves is tolerably 
well defined ; the radius of curvature seeming to depend chiefly 
on the volume of the stream, and the arc of the curve increasing 
as the slope of the stream decreases. May it therefore not be 
possible that as the stream is held in a fixed position at Leeds, 
its lateral oscillations above this point have a maximum value at 
certain distances up stream, and a minimum value, or node of no 
oscillation, at other distances. The fact that the several nodes, 
where the upper terrace plain is broad and the flood-plain is 
narrow, occur at tolerably regular distances lends some color to 
this possibility. 
There is a trifling but interesting example of an encroachment 
upon a small stream by the lateral swinging of the Catskill half 
a mile south of Leeds. The clay-plain, with its thin sandy sur- 
face layer, is here beautifully cut out in a concave curve, the 
manifest work of the Catskill, when its meandering course lay 
further south than now. Such an excavation of the clay-plain 
was the result of gradual cutting on the convex side of the 
stream. Most of the curve is margined by the clay-plain at its 
full normal height ; but at one point there is a gap, and on pass- 
ing south through this, it is found to lead into a small stream 
course, independent of the Catskill at this point, but joining it 
a mile to the southeast. It is clear enough on the ground that 
this little side branch once had a greater length than now, and 
that it then headed up on the normal level of the clay-plain, just 
as its many fellows still do ; but that its original length has been 
decreased by the encroachments of the meandering Catskill. 
The natural dam formed by the Corniferous limestone at Leeds 
has been mentioned as the local controlling baselevel for the 
flood-plain further west. It is clear, however, that the shales of 
the Marcellus valley beneath the ridge of the Corniferous limestone 
and the range of Hamilton bluffs, are excavated distinctly below 
this local baselevel. Part of this excavation may be of glacial 
origin ; but the depth of the gap by which the Kaaterskill 
escapes eastward through the Corniferous ridge a few miles 
further south leads me to believe that part of the excavation was 
preglacial. The cross valley by which the Kaaterskill, a smaller 
stream than the Catskill, turns east to join the Catskill before 
they jointly enter the Hudson is deeper than the notch by which 
the Catskill escapes at Leeds ; and hence the Kaaterskill has 
